<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>0409-01 真·手风琴:hover版</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        body{
            background-color: #ccc;
        }
        .items{
            margin:100px auto;
            width: 1200px;
        }
        .item{
            float: left;
            width: 120px;
            box-sizing: border-box;
            background-color: red;
            border-right: 1px solid yellow;
            height:400px;
            transition: width 0.5s
        }

        .items:hover .item{
            width: 60px;
        }
        .items .item:hover{
            width:660px;   /*会有bug*/
        }
    </style>
</head>
<body>
    <div class="items">
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
    </div>
</body>
</html>